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排序方式: 共有4199条查询结果,搜索用时 15 毫秒
41.
Mun-Soo Yun Ki-Young Jeong Eui-Wan Lee Bong-Soo Jin Seong-In Moon Chil-Hoon Doh 《Korean Journal of Chemical Engineering》2006,23(2):230-236
The aim of this paper is to study the electrochemical behavior of Si-C material synthesized by heating a mixture of silicon
and polyvinylidene fluoride (PVDF) in the ratios of 5, 20, and 50 wt%. The particle size of the synthesized material was found
to be increased with increase in the PVDF ratio. The coexistence of silicon with carbon was confirmed from the XRD analysis.
A field emission scanning electron microscope (FESEM) study performed with the material proved the improvement in coating
efficiency with increase in the PVDF ratio. Coin cells of the type 2025 were made by using the synthesized material, and the
electrochemical properties were studied. An electrode was prepared by using the developed Si-C material. Si-C|Li cells were
made with this electrode. A charge|discharge test was performed for 20 cycles at 0.1 C hour rate. Initial charge and discharge
capacities of Si-C material derived from 20 wt% of PVDF was found to be 1,830 and 526 mAh|g, respectively. Initial charge/discharge
characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216mAh/g at Si-C material
derived from 20 wt% of PVDF, initial intercalation efficiency (IIE), intercalation efficiency at initial charge/discharge,
was 68%. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm * g. 相似文献
42.
Concepts for the effective MWCO of tight-UF membranes, and apparent diffusion coefficients for NOM, were introduced to determine the mechanisms influencing NOM removal and to explain the various behaviors of NOM removal by UF membranes with different hydrophobicities, permeability, and surface charges. Colloidal NOM (COM) and non-colloidal hydrophobic NOM (NCD HP) constituents were chosen for the evaluation of two different UF membranes. For a relatively hydrophobic, relatively high permeability, and less negatively charged UF membrane, the hydrophobic fractions of COM were preferentially removed and were also removed by a size exclusion mechanism (i.e., both hydrophobic interaction and size exclusion mechanisms). The NCD HP exhibited no such preferential removal of the hydrophobic fractions, but could be removed by a size exclusion mechanism (i.e., only size exclusion mechanism). With a relatively hydrophilic, relatively low permeability, and more negatively charged UF membrane, COM exhibited no preferential removal of the hydrophobic fractions, but could be removed by a size exclusion mechanism (i.e., only size exclusion mechanism). Whereas the hydrophobic fractions of the NCD HP were preferentially removed, these could not be removed by a size exclusion mechanism (i.e., only hydrophobic interaction mechanism). The apparent diffusion coefficients of NOM, as determined from NOM diffusion experiments using a diffusion cell equipped with a regenerated cellulose membrane, were much lower than those calculated by the Stokes-Einstein relation. The diffusion coefficient of NOM is expected to be used to predict and explain NOM transport behaviors in tight-UF membranes. 相似文献
43.
Ilsun You Junho Choi Chang Choi Pankoo Kim 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(12):2577-2586
In the field of “U-Healthcare Service”, many studies have been actively conducted to develop “smart device”-based healthcare applications that enable healthcare providers and patients to be better served through interoperations among various kinds of sensors and wireless network interfaces. In particular, contemporary intelligent healthcare services not only recognize users’ context information through smart devices, computers, and so forth, but also acquire information from heterogeneous sensors to achieve context-aware inference services. Among such information, the weather information is tightly related to diseases such as asthma and allergies. Therefore, there is a high demand for research to utilize the weather information for healthcare services. In this paper, we propose a context inference-based intelligent healthcare service that exploits both the weather conditions information and the diverse healthcare ontologies available on the Internet. The proposed service aims at modeling a context ontology in users’ healthcare service environment and defining the inference rules, thereby accomplishing a satisfactory real-time healthcare service. 相似文献
44.
Min Jeong Kim Mina Choi Yong Bum Kim Fengyi Liu Hyungpil Moon Ja Choon Koo Hyouk Ryeol Choi 《International Journal of Control, Automation and Systems》2014,12(2):406-414
This paper proposes a method of exploring the local shape of an unknown object using the force and torque information obtained from active touch. In the first, we present a method to estimate an unknown curvature, using rolling and sliding motion with a force/torque sensor attached to the fingertip of the hand. Then, the normal curvature equation from 2D curvatures is obtained. Finally we present a reconstruction algorithm of local geometry by using a normal curvature equation, which is composed of principal curvatures and principal directions. The method is tested by using a hand-arm system consisting of an industrial robot arm and an anthropomorphic robot hand with 6-axis force/torque sensor. The feasibility of the proposed method is experimentally validated for objects with simple geometries such as cylinder, spheres etc. 相似文献
45.
Young-Ho Lee Shin-Guk Kim Tae-Yong Kuc Jong-Koo Park Sang-Hoon Ji Yong-Seon Moon Young-Jo Cho 《International Journal of Control, Automation and Systems》2014,12(2):390-398
A virtual target tracking approach is proposed for kinematic control of mobile robot. In the controller, linear and angular velocity inputs are generated by using the local data of robot position and orientation along with the estimated velocity of target object. Applying the proposed approach to a cooperative robot group with arbitrary number of multiple mobile robots, it is possible to create various robot formations for cooperative navigation and tracking of moving object. The developed controller is shown to be stable and convergent through theoretical proof and a series of experiments. 相似文献
46.
Shim JH Kim YW Kim TJ Chae HY Park JH Cha H Kim JW Kim YR Schaefer T Spendler T Moon TW Park KH 《Protein engineering, design & selection : PEDS》2004,17(3):205-211
In an effort to improve the properties of cyclodextrin glucanotransferase (CGTase) as an antistaling enzyme, error-prone PCR was used to introduce random mutations into a CGTase cloned from alkalophilic Bacillus sp. I-5 (CGTase I-5). A mutant CGTase[3-18] with the three mutations M234T, F259I and V591A was selected by agar plate assay. Sequence alignment of various CGTases indicated that M234 and F259 are located in the vicinity of the catalytic sites of the enzyme and V591 in the starch binding domain E. The cyclization activity of CGTase[3-18] was dramatically decreased by 10-fold, while the hydrolyzing activity was increased by up to 15-fold. These mutations near subsite +1 (M234T) and at subsite +2 (F259I) are likely to alter the enzyme activity in a concerted manner, promoting hydrolysis of substrate while retarding cyclization. The addition of CGTase[3-18] reduced the retrogradation rate of bread by as much as did the commercial antistaling enzyme Novamyl during 7-day storage at 4 degrees C. No cyclodextrin (CD) was detected in bread treated with CGTase[3-18], whereas 21 mg of CD per 10 g of bread was produced in bread treated with wild-type CGTase. 相似文献
47.
Han Young Moon 《Cement and Concrete Research》2006,36(3):521-529
This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed for three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures and under different environments. The three series of antiwashout underwater concrete were: concrete constituted exclusively by ordinary portland cement (OPC), concrete composed by ordinary portland cement mixed with fly-ash in 20% ratio (FA20) and concrete with ground granulated blast furnace slag is mixed in 50% ratio (BFS50). And, the three different environments were: manufacture in the air, in tap water, and in artificial seawater.Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC manufactured in artificial seawater was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below − 350 mV after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm2 and 0.258%. On the other hand, for the other specimens that are FA20 and BFS50, potential values below − 350 mV were observed later at 18 and 20 cycles, respectively.Results confirmed the expectation that mineral admixtures may be more effective in delaying the development of steel bar corrosion in antiwashout underwater concrete. 相似文献
48.
Moon Sam Shin Ki-Pung Yoo Chul Soo Lee Hwayong Kim 《Korean Journal of Chemical Engineering》2006,23(3):469-475
A multi-fluid nonrandom lattice fluid model with no temperature dependence of close packed volumes of a mer, segment numbers
and energy parameters of pure systems is presented. The multi-fluid nonrandom lattice fluid (MF-NLF) model with the local
composition concept was capable of describing properties for complex systems. However, the MF-NLF model has strong temperature
dependence of energy parameters and segment numbers of pure systems; thus empirical correlations as functions of temperature
were represented for reliable and convenient use in engineering practices. The MF-NLF model without temperature dependence
of pure parameters could not predict thermodynamic properties accurately. It was found that the present model with three parameters
describes quantitatively the vapor pressure and the saturated density for the pure fluid. 相似文献
49.
A novel modified Rayleigh model was developed for compensating hysteresis problem of an atomic force microscope (AFM) scanner.
In high driving fields, piezoelectric actuators that integrated a scanner have severe hysteresis, which can cause serious
displacement errors. Piezoelectric hysteresis is from various origins including movement of defects, grain boundary effects,
and displacement of interfaces. Furthermore, because its characteristic is stochastic, it is almost impossible to predict
the piezoelectric hysteresis analytically. Therefore, it was predicted phenomenologically, which means that the relationship
between inputs and outputs is formulated. The typical phenomenological approach is the Rayleigh model. However, the model
has the discrepancy with experiment result as the fields increase. To overcome the demerit of the Rayleigh model, a modified
Rayleigh model was proposed. In the modified Rayleigh model, each coefficient should be defined differently according to the
field direction due to the increase of the asymmetry in the high fields. By applying an inverse form of this modified Rayleigh
model to an AFM scanner, it is proved that hysteresis can be compensated to a position error of less than 5%. This model has
the merits of reducing complicated fitting procedures and saving computation time compared with the Preisach model. 相似文献
50.
Induced Defensive Response of Myrtle Oak to Foliar Insect Herbivory in Ambient and Elevated Co2 总被引:2,自引:0,他引:2
The rising level of atmospheric CO2 has stimulated several recent studies attempting to predict the effects of increased CO2 on ecological communities. However, most of these studies have been conducted in the benign conditions of the laboratory and in the absence of herbivores. In the current study, we utilized large octagonal chambers, which enclosed portions of an intact scrub-oak community to investigate the interactive effects of CO2 and insect herbivory on myrtle oak, Quercus myrtifolia. Specifically, we assessed the effects of ambient and elevated CO2 (2x current concentrations) on percent foliar nitrogen, C:N ratio, total relative foliar tannin content, and the presence of leaf damage caused by leaf mining and leaf chewing insects that feed on myrtle oak. Total foliar N declined and C:N ratios increased significantly in oaks in elevated CO2 chambers. The percentages of leaves damaged by either leafminers or leaf chewers tended to be lower in elevated compared to ambient chambers, but they co-occurred on leaves less than expected, regardless of CO2 treatment. Leaves that had been either mined or chewed exhibited a similar wounding or defensive response; they had an average of 25 and 21% higher protein binding ability, which is correlated with tannin concentration, compared to nondamaged control leaves, respectively. While the protein-binding ability (expressed as total percent tannin) of leaves from elevated CO2 was slightly higher than from leaves grown in ambient chambers, this difference was not significant. 相似文献